Mozilla Corp.'s Firefox browser finished the year with a flourish, a Web measurement firm said Wednesday, and came within half a point of the 10 percent market share that many analysts have set as the bar to long-term success against Microsoft's leading Internet Explorer.

According to the latest numbers from Aliso Viejo, Calif.-based NetApplications, Firefox wrapped up 2005 with 9.6 percent of the browser market, a gain of almost a full point over November.

"Firefox is very close to hitting a critical mass of 10 percent, which could mean a more rapid adoption rate," said Vince Vizzaccaro, vice president of marketing at NetApplications, in a statement.

Although first-generation Firefox 1.x accounted for the bulk of the open-source browser's market share, the newest edition, Firefox 1.5, which went final in late November, gained ground in December. The last month of the year, said NetApplications, Firefox 1.5 was used by 2.5 percent of surfers, an impressive increase over November's 0.3 percent.

Microsoft's Internet Explorer continued to slip in December, falling to 85 percent from November's 86.1 percent. In the last 12 months, IE has lost five percentage points in the browser battle.

"But IE won’t go away quietly," cautioned Vizzaccaro. "Long overdue upgrades are expected to be released in 2006."